> I caused like a 20-30% regression in JS performance on ARM by changing one atomic variable in the engine to sequentially-consistent instead of release-acquire.
Very interesting. Was this overall performance? What type of workload was involved?
Yeah it seems like acq-rel is the only other one worth keeping an eye out for. When using atomics you have different logical ops with a certain happens-before relation between them anyway. Figuring out whether these ops map to acq-rel seems like a reasonable task to take on, given the total effort. The main argument against it is lack of testing infrastructure (since indeed correctness is more important). With something like Loom (the Rust project) it’s significantly easier to prevent subtle bugs. I wish it was more widely available.
Very interesting. Was this overall performance? What type of workload was involved?
Yeah it seems like acq-rel is the only other one worth keeping an eye out for. When using atomics you have different logical ops with a certain happens-before relation between them anyway. Figuring out whether these ops map to acq-rel seems like a reasonable task to take on, given the total effort. The main argument against it is lack of testing infrastructure (since indeed correctness is more important). With something like Loom (the Rust project) it’s significantly easier to prevent subtle bugs. I wish it was more widely available.